According to Autocar, the project will benefit from the experience Toyota gained with the TS030, its hybridized Le Mans prototype. The evidence for this is, of all things, a Toyota Yaris - in particular, the Yaris Hybrid R that was shown at the 2013 Frankfurt Motor Show last September. That car used a 300-horsepower, 1.6-liter gas engine, while a pair of 60-horsepower electric motors provided all-wheel-drive push (an additional motor also sent additional juice to the front axle). The 414-system-horsepower drivetrain used supercapacitors in place of the traditional lithium-ion batteries of traditional hybrids.

For the production sports cars, Autocar claims that the Yaris Hybrid R's setup will serve as the basis for the new powertrain, although it won't be a direct carryover. Instead, a 2.0-liter BMW engine will be paired with Toyota-designed, BMW-built motors.

While Toyota will be responsible for making the new car go, BMW will handle the car's structure and body. Carbon-fiber reinforced plastic, high-strength steel and aluminum will all play major roles in the construction, according to AC, with a low curb weight being a high priority.

This all sounds rather far-fetched to us, largely because of the existence of the BMW i8. That car already generates 362 system horsepower and 420 pound-feet of torque from a plug-in drivetrain, and it also benefits from extensive use of CFRP and aluminum. Finally, the i8 retails for six figures. Building the Z4 replacement that Autocar describes and keeping it around the current car's price simply doesn't seem possible. Besides that, the idea of an all-wheel-drive Z4 kind of runs counter to what the Z4 is, an old-school, cab-backwards rear-drive roadster.